Why is it harder and harder for people to remember things as they get older? Is it because their brain is full?

Not so, according to a Johns Hopkins neuroscientist:

According to a Johns Hopkins neuroscientist, however, the real trouble is that our aging brains are unable to process this information as "new" because the brain pathways leading to the hippocampus -- the area of the brain that stores memories -- become degraded over time. As a result, our brains cannot accurately "file" new information (like where we left the car that particular morning), and confusion results.

"Our research uses brain imaging techniques that investigate both the brain's functional and structural integrity to demonstrate that age is associated with a reduction in the hippocampus's ability to do its job, and this is related to the reduced input it is getting from the rest of the brain," said Michael Yassa, assistant professor of psychological and brain sciences in Johns Hopkins' Krieger School of Arts and Sciences. "As we get older, we are much more susceptible to 'interference' from older memories than we are when we are younger."

In other words, when faced with an experience similar to what it has encountered before, such as parking the car, our brain tends to recall old information it already has stored instead of filing new information and being able to retrieve that. The result? You can't find your car immediately and find yourself wandering the parking lot."Maybe this is also why we tend to reminisce so much more as we get older: because it is easier to recall old memories than make new ones," Yassa speculated.

So when you see me repost things that have been on Neatorama before, this may just be the reason: Link

This may be misleading. We all have a tendency to reflect on what we already know and slot our new experiences in with the old. It doesn't matter if you are 8 years old or 80 years old, except that when you are 80 you already have a model of the world which you think covers just about everything.

I think the causes for this are complex and require an understanding of the representational structure of the brain generally, as well as the process of synaptic plasticity which allow for the formation of new representations and solidification of old representations.

Alzheimer's disease has been associated with an amyloid plaque build-up in the brain which can be largely postponed by keeping the brain in a state of flux. If one gets too routinized and doesn't learn new information, but repeats the same too-tired categories, thoughts and opinions, then one "hardens" the brain into that rigid pattern of activation with little chance of restructuring it.

Generally, the tendency to compress new information to fit into existing models of the world is known as confirmation bias, categorical thinking and closed-mindedness. The inability to assess new information in old age may simply be the natural consequence of having a self-centered bias in the formation of the model to begin with.

I want to stress that as far as representational neuroscientists are concerned the whole of representational space must be coherent, when new information threatens the coherence of the world-model, the system has to account for the new information and we experience discomfort, uncertainty, insecurity and despair. A number of factors that force us to find a new coherent model to continue on our lives. We will sit by ourselves, pitifully, trying to rethink our world until it makes sense. It is much easier, therefor, to make everything fit into the current model if at all possible, the job of recreating the model to be congruent with the new information is unpleasant and energy-consuming.